Many types of on-site sewage treatment plants are available which aim to continuously treat raw sewage and to discharge the treated effluent at a quality which can be safely and effectively discharged as a sub-soil discharge or as a surface discharge onto a dedicated soakage area. If effective treatment is not achieved, discharge of the treated effluent can cause hygiene problems, unpleasant odours, contamination of the environment and reduced cycle time between required periodical refurbishing of the on-site treatment plant and/or the discharge treatment.
While the problems associated with underperforming on-site sewage treatment plants is clear its solution is not, as it is not feasible to regularly dispatch trained personnel to test and monitor each on-site treatment plant for discharged effluent quality at a required standard. Furthermore assembling a meaningful database of information concerning the performance of on-site sewage treatment plants in a manner which may be readily used to assist decision-making in an attempt to improve a local environment is not currently practical.
Typically, discharged treated effluent is evaluated by measuring the percentage of total suspended solids (TSS) and/or biochemical oxygen demand (BOD) which is commonly measured over a five day period (BOD 5) and is widely used as a standard for evaluating a test sample. These tests, which require analysis in a laboratory, are expensive to conduct and take time to achieve a result which can be acted upon to rectify an underperforming treatment plant.
In an attempt to circumvent this problem, discharged treated effluent quality testing is often carried out by a trained analyst making a visual examination of the discharged treated effluent. This analyst based evaluation method is problematic since the test results are based on the analyst's skills. As a result there is no strict adherence to a standard and thus a treatment plant given a pass evaluation by one analyst may be rated as a fail evaluation by another analyst. Furthermore, the collection of data gathered by such methods does not provide an effective overview of the performance of on-site treatment plants in a given area on which sound decisions can be made with a view to improving the health of the populating citizen's environment. In addition, unscrupulous operators can easily provide incorrect information which may make gathered information unreliable.
This invention aims to provide a method of and/or apparatus for monitoring a characteristic of a liquid/fluid sample which will alleviate one or more of the disadvantages associated with the presently available methods, some of which are set out above.